1. Field of the Invention
This invention relates in general to rocket ramjet engines and more particularly to boost phase survivable fuel injectors and flameholders for use with rocket ramjet engine.
2. Discussion of the Prior Art
It is already known to provide an engine which comprises a rocket engine and ramjet engine having a common combustion chamber for both types of operation. Conventional and integral rocket ramjet engines commonly use two types of fuel, each during a different phase of operation. In the initial rocket operation or boost phase, a solid propellant charge which contains an oxidizing material burns upon ignition by an igniting means. Exhaust gases pass through a jet nozzle and propel the rocket with a large amount of thrust. The amount of thrust depends upon several factors such as nozzle design, propellant type, propellant density, and the surface area of the propellant exposed to burning. The solid propellant charge which is generally located in the aft end of the rocket may have an axial bore which exposes more than just the end surface area of the charge to burning and therefore yields more thrust. During the rocket operation, or boost stage, the solid propellant does not need rammed air for proper operation. The solid propellant contains enough oxidizing material in itself to support combustion.
Upon exhaustion of the solid propellant, the boost phase is ended and the ramjet operation or sustain phase begins. During the sustain phase, the projectile is propelled by a fuel charge which is not capable of burning without an outside source of oxygen. After the boost phase is completed, therefore, air is rammed into the rocket's combustion chamber through inlet ducts or ports. Initially the ports are closed during the boost phase. The rammed air admitted to the combustion chamber reacts with the fuel charge to sustain the rocket in flight. The fuel charge, normally a liquid or a slurry, will be injected into the stream of rammed air. The air and fuel combust, and the exhaust gases pass through a nozzle, providing thrust for sustaining the projectile in flight.
One efficient packaging design for integral rocket-ramjets is described in Ser. No. 582,956, Brousseau, et.al., Loaded Air Duct Integral Rocket Ramjet, filed June 2, 1975. The rammed air inlet duct is used to initially package a portion of boost propellant. Ramjet operation subsequent to the boost burnout requires that certain elements such as flameholders and some fuel injectors be located physically within the inlet duct at or just upstream of the entrance to the combustion chamber. These elements are fixed position devices and require physical protection from the internal boost phase environment to permit them to function satisfactorily in the subsequent ramjet mode.
The prior art discloses the concept of having an element such as a fuel injector within a body of solid boost propellant which is cast thereabout as shown in U.S. Pat. No. 3,325,998; and U.S. Pat. No. 3,482,403. No protective means for these elements are disclosed however.